Proximal cable-less communication system with intentional signal path

ABSTRACT

An improved proximal cable-less communications system using at least two receivers is described. The system is significantly improved by utilizing an intentional signal path for the local oscillator signal to be radiated while maintaining the architecture of each receiver and the proximal cable-less communications system. The effectiveness of radiation can be increased by extending the length of the electrical interconnect which connects the local oscillator to the mixer. In addition, the effectiveness of radiation is increased by magnetically coupling the electrical interconnect which connects the local oscillator with the mixer with the electrical interconnect which connects the antenna and the mixer. By coupling the two electrical interconnect, the signal output by the local oscillator is induced on the electrical interconnect between the antenna and the mixer. The coupling is set such that the signal induced travels along the electrical interconnect and is radiated out of the antenna.

BACKGROUND OF THE INVENTION

1. FIELD OF THE INVENTION:

The present invention released to the field of proximal cable-lesscommunication systems.

2. RELATED APPLICATIONS

This application is related to U.S. patent application Ser. No.07/477,680, filed Feb. 9, 1990, entitled "Parametrically TunedOscillator", now abandoned. U.S. Pat. No. 5,032,802, entitled "HybridDirectional Coupler Circuit", U.S. patent application Ser. No.07/477,632, filed Feb. 9, 1990, entitled "Method and Apparatus forIncreased Receiver Sensitivity in a Proximal Cable-less CommunicationSystem", U.S. patent application Ser. No. 07/478,220, filed Feb. 9,1990, entitled "Method and Apparatus for Selective Sideband in aProximal Cableless Communication System Signal", which are incorporatedby reference.

3. ART BACKGROUND:

In the class of short-range (approximately 500 ft.) transceivers, suchas cordless telephones or "walkie-talkies", basic super heterodynetechniques are used to receive an incoming signal and mix it with alocal oscillator to provide an intermediate frequency (IF). The IF isdetected and the resulting signal, such as voice, is amplified for enduse. In transmission, the same transceiver unit accepts an input, suchas voice, and modulates a carrier frequency. The resulting modulationenvelope is amplified in the power amplifier for transmission.

Transmission of signals between two short-range transceivers stillrequires communication over a distance. To provide signal transferacross this distance, a nominal power level is required for transmissionof intelligence. Such transmission would require a similar circuit asdescribed above. When the distance is much shorter, communication may beachieved over lines or cable. Such direct physical connections are usedbecause of simplicity and cost savings. However, physical connectionssignificantly restrict the mobility of the users of the transceivers.

In U.S. Pat. No. 4,759,078, a proximal cable-less communications systemusing two receivers is described. A local oscillator of the firstreceiver is modulated to convey intelligence to a second receiverthrough the leakage radiation from the first local oscillator.Similarly, the local oscillator of the second receiver may also bemodulated whereby the first receiver detects the leakage radiation fromthe local oscillator of the second receiver. The intermediatefrequencies of the two receivers are set to frequencies such that thelocal oscillators provide the input signals to a mixer which generatessignals at the intermediate frequency from which information isextracted. By proximately disposing the two receivers to each other,two-way transfer of information is achieved.

Using this approach, two way communication is achieved within a limitedrange without the need for complicated circuitry to provide thetransmission of signals. Further, it permits a significant increase inuser mobility.

This system is described by referring to the diagram of FIG. 1. Two waycommunication is achieved by tuning local oscillator (LO) 11 to a firstfrequency and LO 21 to a second frequency. Antenna 23 is tuned toreceive the LO 11 frequency and antenna 13 is tuned to receive the LO 21frequency. The intermediate frequency (IF) for both units 10 and 20 aredetermined by the difference of the frequencies of the two LOs, 11 and21. The frequencies of the LOs 11 and 21 are set so that theirdifference is equal to the IF of both receiving systems.

Because of the proximity of the receivers to each other, antennae 13 and23 are capable of receiving radiation from opposing LOs 21 and 11,respectively. Therefore, antenna 23 receives the first frequencyradiation of LO 11 and mixes the signal with the second frequency fromLO 21 in mixer 22 to provide an IF to Block 24. Correspondingly, antenna13 receives the second frequency radiation from LO 21 and mixes thesignal with the first frequency radiation from LO 11 in mixer 12 toprovide the IF to block 14. By providing intelligence through themodulation of LO 11 and 21 signals, communication may be achievedbetween the units 10 and 20.

This system is inherently limited to modest power levels, namely theavailable local oscillator power, which clearly dictates the proximalrange for the system. Furthermore, this system lends itself toapplications inside buildings, as opposed to outdoor applications. Assuch, the performance is affected by the confines and obstructionswithin the building. For example, the propagation model for outsideimplementation might be close to free space or 1/r² (where r is theradial distance), whereas in-building proximal systems may have apropagation model as restrictive as 1/r⁴. Thus, given the same sourcepower, the effectiveness of the system may suffer a 30 dB loss at anapproximate frequency of 1500 MHz over a 30 meter range. This loss ofeffectiveness is even more evident at UHF and higher, where path loss ismore significant.

In addition, when the modulator (e.g., modulator 16 in receiver 10 ofFIG. 1) is operating, and modulating the local oscillator (e.g. LO 11),and an incoming signal is detected, the signal received which is mixedwith the modulated signal output by the local oscillator is somewhatdistorted or contaminated by the modulation imposed on the oscillator.This distortion is referred to as sidetone. Although this feature is notalways a problem, it is a hindrance when implementing digital systemsand analog systems where sidetone is undesired, such as when thesidetone is significant to affect the value of the output information.

Summary of the Invention

It is therefore an object of the present invention to present animproved proximal cable-less communications system which has little orno sidetone.

Furthermore, it is an object of the present invention to provide aproximal cable-less communications system which effectively radiates theminimal local oscillator signal.

It is an object of the present invention to provide a proximalcable-less communication system which allows a more selective andsensitive receiver to be implemented to enhance the performance of thesystem.

An improved proximal cable-less communications system using at least tworeceivers is described. The system is significantly improved byutilizing an intentional signal path for the local oscillator signal tobe radiated while maintaining the architecture of each receiver and theproximal cable-less communications system. The receiver performance isalso improved by including a preselection filter to eliminate extraneoussignals, particularly signals at the image frequency of the mixer. Inaddition, an amplifier is utilized to further enhance the signalresulting in a more selective and sensitive receiver.

Furthermore, in the improved proximal cable-less communication system ofthe present invention, sidetone is eliminated through the use ofcomponents, placed after mixer which generates signals at theintermediate frequency and prior to detection device of the informationencoded in the signals at the intermediate frequency, which cancel outthe effect of those signals containing information derived from themodulation of the local oscillator of each receiver of proximalcable-less communication system of the present invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The objects, features and advantages of the present invention will beapparent from the following detailed description of the invention inwhich:

FIG. 1 is a block diagram of the prior art proximal cable-lesscommunication system.

FIGS. 2a, 2b and 2c are block diagrams of the improved proximalcable-less communication system of the present invention which utilizesan intentional signal path while maintaining the architecture of theproximal cable-less communications system.

FIG. 3 is a block diagram of the improved proximal cable-lesscommunication system of the present invention which improves receiverperformance a preselection filter and amplifier to provide a moreeffective receiver.

FIG. 4 illustrates an example of the frequency spectrum of thepreselection filter employed in the second embodiment of the presentinvention.

FIG. 5 is a block diagram of another embodiment of the improved proximalcable-less communication system of the present invention which employsbinary phase shift keying (BPSK) to eliminate sidetone.

FIG. 6 is a block diagram of another embodiment of the improved proximalcable-less communication system of the present invention employingfrequency shift keying (FSK) circuitry to eliminate sidetone.

FIGS. 7a and 7b are block diagrams of still another embodiment of theimproved proximal cable-less communication system of the presentinvention which employs a processor to perform intelligentsynchronization of the modulation of the local oscillator and thereceipt of a modulated signal from a second receiver.

FIG. 8 is a block diagram of another embodiment of the improved proximalcable-less communication system of the present invention whicheliminates sidetone through the synchronization of baseband and sidebandsignal generation and reception.

FIGS. 9a, 9b and 9c illustrate a first exemplary improved proximalcable-less communication system of the present invention.

FIGS. 10a and 10b illustrate a second exemplary improved proximalcable-less communication system of the present invention.

FIGS. 11a and 11b illustrate a third exemplary improved proximalcable-less communication system of the present invention.

FIGS. 12a and 12b illustrate a fourth exemplary improved proximalcable-less communication system of the present invention.

FIGS. 13a and 13b illustrate a fifth exemplary improved proximalcable-less communication system of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

An improved proximal cable-less communication system is hereindescribed. Referring to FIG. 2, the receiver device maintains theprimary function of its local oscillator to provide a signal having apredetermined frequency into the mixer and utilizes an intentionalsignal path to improve the receiver's secondary function, incidental tothe primary function of the local oscillator of the receiver, to moreeffectively radiate the information to be conveyed by the receivingdevice through the leakage radiation which emanates from the localoscillator within the receiver.

FIG. 2a shows a first embodiment in which the local oscillator 120 isinput to mixer 160 to provide a signal at first a predeterminedfrequency into the mixer 160. A signal at a second predeterminedfrequency is received by antenna 150 and is input to mixer 160. Thereceived signal is a modulated signal preferably radiated by a secondreceiver, similarly configured, the modulation of the signal conveyinginformation which is subsequently decoded as the output of the receiver.The mixer 160 generates a signal at the frequency which is the sum ofthe frequencies of the two input signals ("the sum frequency") and atthe frequency which is the difference of the frequencies of the twoinput signals ("the difference frequency"). The difference frequency,referred to as the intermediate frequency (IF), is passed through as anintermediate frequency detector which detects the modulation of thesignal originating from the modulated received signal and produces thedata output 180. In addition to providing the signal that is mixed withthe received signal to generate the intermediate frequency signal, localoscillator 120 may also be used to communicate information throughmodulation of the signal generated by local oscillator 120.

To cause a more effective radiation of the signal generated by localoscillator 120 without affecting the signal input to mixer 160, anintentional signal path is used to promote radiation of the localoscillator signal. In the embodiment represented by FIG. 2a. A firstelectrical interconnect (e.g. signal line or signal wire) which connectsthe local oscillator 120 and mixer 160 is intentionally routed to lieparallel with and in close proximity to a second electrical interconnectwhich connects the antenna 150 and mixer 160. The length the twoelectrical interconnect are parallel and the distance the two electricalinterconnect are separated must be sufficient that a signal on the firstelectrical interconnect is imposed on the second electrical throughinductive coupling of the two electrical interconnect. Preferably theminimum length the electrical interconnect are parallel is approximatelyequal to one-tenth of the wave length. For example, at a frequency of2.4 GHz, it is preferred that the electrical interconnect are parallelfor approximately 0.5 inches. The spacing between the electricalinterconnect should be as small as possible. For example, the spacingshould be 0.1 inches. Thus, the primary function of the localoscillator--to provide a signal into the mixer 160--is maintained andthe modulated signal output by local oscillator 120 is more effectivelyradiated by radiating the signal through antenna 150 via the inductivecoupling between the electrical interconnect connecting local oscillator120 to mixer 160 and antenna 150 to local oscillator 160.

The length of the first electrical interconnect can also be increased tofurther provide opportunity for the signal output by local oscillator120 to radiate by providing additional electrical interconnect for thesignal to leak from. FIG. 2b illustrates another embodiment of thepresent invention which more effectively radiates the leakage radiationof the local oscillator 120 using an intentional signal path thataccentuates the leakage radiation of the signal output by localoscillator 120 while providing its primary function, that of providingan oscillating signal at a predetermined frequency to mixer 160.

In this embodiment, the signal generated by local oscillator 120 isinput to a hybrid directional coupler 135 which couples the signal inputby local oscillator 120, directing the signal to mixer 160 and toantenna 150. Furthermore, the hybrid directional coupler couples thesignal received through antenna 150 to the mixer 160 with the minimum ofpower loss. The hybrid directional coupler is described in U.S. Pat. No.5,032,802, entitled "Hybrid Directional Coupler".

Another embodiment is illustrated by FIG. 2c. FIG. 2c shows a system inwhich the data in 100 is input to modulator 110, which modulates localoscillator 120 thereby encoding the data in 100 on the signal output bylocal oscillator 120. The signal output by local oscillator 120 is usedas one of the inputs to mixer 160. The second input to mixer 160 is thesignal detected and received by antenna 150. The mixer generates anintermediate frequency containing data encoded on the signal receivedthrough antenna 150. The encoded information is detected by IF detector170 to generate the data output 180. Local oscillator 120 is also usedto radiate information encoded on the oscillating signal by modulator110 through its leakage radiation. Rather than letting the leakageradiation be radiated in a undirected manner, the radiation iseffectively directed to splitter 130, which splits the signal betweenthe mixer 160 and a second antenna 140. Antenna 140 is separate from thereceiving antenna 150 and radiates the modulated signal informationgenerated by local oscillator 120 thereby increasing the effectivenessof the radiation while maintaining the architecture of the receiverdevice and the primary function of the local oscillator.

By using an intentional signal path through a separate antenna,flexibility in the arrangement of the antennae is provided to maximizeefficiency reception and radiation of signals into the receiver of thepresent invention. Specifically, by using a two antenna configuration,the antennae can be arranged to maximize the discrimination ability ofthe receiving antenna and maximize the radiating efficiency of theradiating antenna (and therefore the local oscillator). In the receiverof the present invention, the capability to more effectivelydiscriminate all signals except the intended received signal becomescritical because of the increase effectiveness of radiation of the localoscillator signal. The increase in the radiation efficiency of the localoscillator will, as a consequence, also increase the interference of thelocal oscillator's signal on the signals detected at the receivingantenna. This undesirable effect is referred to as front end overload.The antennae can be placed physically apart from one another to decreasethe effect the signal intentionally radiated through the first antenna(e.g. antenna 140, FIG. 2c) has on the signals received through thereceiving antenna (antenna 150, FIG. 2c). Preferably the antennae arespaced a minimum distance approximately equal to one-half of the localoscillator signal wave length. For example, at a signal frequency of 2.4GHz, the antennae are preferably spaced apart a minimum distance of 2.5inches.

The front end overload may also be decreased by having the receivingantenna at a polarization different from the polarization of theradiating antenna. It has been found that, on the average, a 20 dBdiscrimination occurs between antennae of different polarization. Thereceiving antenna can, for example, be horizontally polarized and theradiating antenna can be vertically polarized whereby the front endoverload induced by the signals radiated by the radiating antenna areattenuated by 20 dB.

The two antennae may be of different size and lengths in order tooptimize each antenna's function. For example, a relatively shortantenna can be used to receive signals, because it is not used toradiate signals but only receive signals, while a relatively longantenna is used to radiate signals such that there is less loading onthe antenna resulting in a more efficient radiator.

In another implementation which utilizes two antennae, the two antennaeare established in a colinear arrangement (end to end). This creates awave pattern such that interference of signals received and radiated isminimal because the two antennae lie in each other's radiation minima.

Furthermore, by using a two-antenna receiver of the present invention,each antenna can be highly tuned to the frequency each is to receive orradiate. The antennae are more efficient in their functions because thbandwidth of signals to which each antenna is tuned is narrow and thereceiver antenna discriminates against frequencies except the knownreceiving frequency. The receiver antenna therefore discriminatesagainst the signals at the frequency generated by the local oscillatorof the receiver, thereby reducing the front end overload.

Referring to FIG. 3, another improvement to the proximal cablelesscommunications system is described. As described above, the antenna 150receives leakage radiation from the local oscillator of a secondreceiver device, similarly configured, wherein the local oscillator ismodulated according to the data input to the second receiver device.

The intermediate frequency is increased to provide a greater separationof the frequencies of the local oscillators of the receiver devices suchthat frequency preselection is achieved using simple, low costcomponents. In addition, a filter and an amplifier are used to providethat only the intended received signal is processed through thereceiver, thereby eliminating extraneous signals which can causecorruption of the signal and the final information output.

In the system of the present invention, a more selective and sensitivereceiver is provided. The intermediate frequency is increased to providea greater separation between the frequencies of the signals generated bythe local oscillators of the receiver devices. By providing a greatermargin, the signal processing process is simplified and simpler low costcomponents may be employed to process the signal because the margin forerror is increased. For example, it is preferred that a 50 MHzseparation is provided between local oscillator frequencies in the rangeof 2000-3000 MHz.

The signal received by antenna 150 is input to a filter 190 whichfilters out frequencies which do not contain the information radiatedfrom a second receiver device. The signal is then input to amplifier200, which amplifies the signal and provides for increased sensitivityof the signal by the IF detector 170. The filter 190 acts as a signalpreselection device. This filter can be defined according toapplication. For example, if the local oscillator is below the frequencyof the desired receiving frequency, the filter may be defined to be ahigh pass filter, thereby eliminating the low frequency signals from thelocal oscillator. Preferably the filter is a band pass filter designedto center around the frequency of the received signal, that is, thefrequency of the local oscillator of the second receiver device.

By designing the filter to center around the receiving frequency andincreasing the intermediate frequency, a simple, low cost, but accuratepreselection device is provided which attenuates the undesired signals,including the signals generated by the local oscillator of the samereceiver. The filter also attenuates those signals at the imagefrequency of the intermediate frequency. The mixer generates signals atthe frequencies which are the sum and difference of the inputfrequencies. The difference frequency is the intermediate frequency.However, for any given input frequency there are two frequencies which,if input to a mixer with the given input frequency, generates theintermediate frequency. For example, if the received signal is at afrequency of 2400 MHz and the local oscillator in the receiver generatesa signal at a frequency of 2450 MHz, the sum frequency output by themixer would be 4850 MHz and difference frequency, that is, theintermediate frequency, would be a frequency of 50 MHz. However, for alocal oscillator having a local oscillating frequency of 2450 MHz, asignal at a receiving frequency of 2500 MHz will also cause the mixer togenerate an intermediate frequency of 50 MHz. This frequency is referredto as the image frequency.

An exemplary filter function is represented by FIG. 4. In the presentexample, the local oscillator of a first receiver constructed accordingto the receiver of the present invention is tuned to a frequency in therange of 2451-2482 MHz to receive signals in the range of 2401-2432 MHz.The local oscillator of a second receiver also constructed according tothe receiver of the present invention is tuned to a frequency in therange of 2401-2432 MHz to receive signals in the range of 2451-2482 MHz.Thus, the intermediate or difference frequency occurring at the outputof the mixer is 50 MHz. The bandpass filter shown is designed to be usedin both receivers; therefore the filter has a bandwidth wide enough topass signals at the frequencies the local oscillators of the receiversare tuned to, but narrow enough to attenuate extraneous signals such assignals at the image frequencies. Similarly the bandpass filter can bedesigned to a narrower bandwidth such that the passband centers aroundthe receive frequency only, thereby attenuating signals at the frequencyof the local oscillator of the same receiver.

By using the preselection filter 190 (FIG. 3), the influence of thelocal oscillator of the receiving device, which is most often a strongersignal than the signal originating from the local oscillator of thesecond receiver device and received through antenna 150, is greatlyreduced. The preselection filter 190 enhances signal image rejection inthe receiver and lessons the possibility of densensitization of themixer 160 caused by the presence of radiation from the local oscillator120 (front end overload). In addition, the amplifier 200 amplifies theincoming signal to provide a stronger signal into mixer 160, therebyincreasing the sensitivity of the receiver and improving the performanceof the communications link between two receiver devices constructedaccording to the architecture of the proximal cable-less communicationsystem of the present invention.

As discussed earlier, when operating the proximal cable-lesscommunications system in duplex mode (i.e. when modulating the localoscillator and receiving signals through the antenna concurrently)sidetone is produced. In digital systems this is undesirable because thesidetone may corrupt the signal significantly to change the state of thedigital output, for example, from a value of 0 to a value of 1. Anotherimprovement of the system of the present invention is the elimination ofsidetone in full duplex proximal cable-less communication systems. Inthe receiver device as shown in FIG. 5, a binary phase shift keying(BPSK) circuit 220 comprising a local oscillator is configured to shiftthe oscillating signal according to the data input which functions as acontrol signal. For example, the BPSK 220 circuit can be configured toshift the oscillating signal by 180 degrees if the data input is a valueof 1 and by 0 degrees (i.e. not shift the phase of the signal) if thedata input is a value of 0. According to the control signal input, theBPSK circuit to 220 will perform a phase shift accordingly to encodeintelligence into the local oscillating signal.

The output of the BPSK circuit 220 is input to a network 240, whichsplits the signal and outputs the signal to antenna to 260 for radiationand subsequent detection by a second receiver device similarlyconfigured. Network 260 also outputs the signal to mixer 270 for use indetecting data received through the signals received by antenna 260.Preferably, the signal is a hybrid directional coupler as shown in FIG.5. In the present illustration a double frequency conversion circuit isutilized to adjust the final intermediate frequency to a frequencyacceptable to IF amplifier-detector 310. In a double conversion circuitthe signal received is processed through two mixers. The first mixer 270performs the mixing function to generate a first intermediate frequency(IF) which is input to a second mixer 280. The data input 230 is alsoinput to a second BPSK circuit 290, which comprises a local oscillatorgenerating a second oscillating signal at a different same frequency asthe local oscillator in BPSK circuit 220. BPSK circuit 290 shifts thephase of the local oscillating signal opposite to the phase shiftgenerated by BPSK circuit 220. The second BPSK circuit 290 is configuredto function in opposition to the first BPSK circuit 220 such that outthe modulated local oscillating signal generated by local oscillator 210is cancelled out in mixer 280.

For example, in the present illustration, the second BPSK circuit willbe configured to shift the input oscillating signal by 180 degrees whenthe data input is the value of 0, and shift the input oscillating signalby 0 degrees when the data input value is 1. When the signal output bythe first mixer 220 is mixed, via the second mixer 280, with the outputof the second BPSK circuit 290, the output by BPSK circuit 290 cancelsout the portion of the signal contributed by BPSK circuit 220 and localoscillator 210, which is considered to be sidetone. Consequently, thesignal input to IF detector 310 is a clean signal without sidetone thedata output therefrom (320) and can be easily detected.

Another method for sidetone correction is described with reference toFIG. 6. Although this embodiment is described utilizing a two-antennasystem, the system is not limited as such and can also operate using asingle antenna. The data in 350 is used to control a frequency shift keycircuit (FSK) 370 which causes the oscillating signal output by thelocal oscillator contained in the circuit to be shifted in frequencyaccording to the data input 350 values. For example, when the data inputvalue is equal to zero there is no shift in frequency and when the datainput value is the value of 1 the frequency is shifted by apredetermined amount. The output of FSK circuit 370 is input to a signalsplitter 380 which outputs the modulated signal to antenna 390 forradiation and to mixer 400. Mixer 400 also receives as input thosesignals detected and received by antenna 410. The output of the mixer400 is a first intermediate frequency signal which is a combination ofthe modulated signal output by FSK circuit 370 and the signal detectedand received by antenna 410. To eliminate the sidetone caused by themodulation of local oscillator 360, the same data input 350 is input toan inverted frequency shift keying circuit (FSK⁻¹) 420. FSK⁻¹ circuit420 modulates a local oscillator contained therein, which operates atthe same frequency as the local oscillator contained in FSK circuit 370and causes the frequency of the signal output to be shifted the sameamount as the signal output by FSK circuit 370 in the opposite directionaccording to the data input 350.

In the present example FSK circuit 420 would modulate the localoscillator to produce a signal which shifts the oscillating signal bythe same amount as FSK circuit 370, but in the opposite direction. Thismodulated signal output by FSK⁻¹ circuit 420 is input to mixer 440 whichproduces the intermediate frequency signal without sidetone because themodulated signal generated through FSK circuit 370 is substantiallycancelled out by the modulated signal generated through FSK⁻¹ circuit420 (the FSK⁻¹ circuit 420 may not cause complete cancellation of thesidetone of the signal generated by FSK circuit 370 due to slightinaccuracies in circuit construction). The signal output from the mixer440 is then input to an intermediate frequency detector which detectsthe intelligence encoded therein and outputs the data 460.

Another embodiment for the elimination of sidetone is illustrated by theblock diagram of FIG. 7a. In this method, cancellation of the sidetoneis achieved through a digital system which utilizes a microprocessordevice and a decoder and the implementation of an intelligent connectionbetween the sourcing microprocessor and the local decoder. The systemdescribed herein is digital in operation. Although not shown by thefollowing figures, the data input to the microprocessor is in a digital(preferably binary) format. Therefore, any analog data input, forexample voice, must be first converted from analog format to a digitalformat. This may be achieved by a widely available analog to digital(A/D) converter. Similarly, if the final data output is to be in theformat of analog signals, the data output from the decoder must be inputto a digital to analog (D/A) converter to convert the output fromdigital format to analog format.

Referring to FIG. 7a, the data input 470 is input to microprocessor 480,which performs two primary functions. One function of the microprocessor480 is to send the intended output data to local oscillator 490, wherethe local oscillator is modulated by the data and, in turn, radiated forreception by a second receiving device through the leakage radiation ofthe local oscillator. Data encoded on signals radiated by the secondreceiver device are received through antenna 500 and input to mixer 510,which mixes the received signals with the signal output by localoscillator 490. This produces intermediate frequency signals containinginformation encoded by the second receiver. If the local oscillator 490is modulated at the same time as the local oscillator in this secondreceiver, the output data encoded by the signals radiated by the secondreceiver, received through antenna 500 and, input to mixer 510, will becorrupted, unless the output of mixer 510 is corrected to compensate forthe concurrent modulation of local oscillator 490. This is performed bytiming the transfer of the input data 470 from microprocessor 480 todecoder 530, either by microprocessor 480, or through external delaycircuits, to arrive at the decoder 530 at the same time as thecorresponding information from IF detector 520 arrives which comprisesdetected signals received from a second receiver device through antenna500 as mixed with the signals generated by local oscillator 490modulated by the data input 470. The decoder decodes the informationreceived from the IF detector 520 and, using the information receivedfrom microprocessor 480, cancels out the effect, if any, caused by themodulation of local oscillator 490 through binary logic operations. Thedesired data from the second receiver is output as the data output 540.

Still another embodiment for the elimination of sidetone is illustratedby block diagram FIG. 7b. It should be noted that the main differencebetween FIG. 7a and FIG. 7b is the direction of data flow between themicroprocessor 480 and decoder 530. In this method, intelligentsynchronization is achieved between the data encoded and output throughthe leakage radiation of local oscillator 490 and the data encoded onsignals received by the antenna 500, such that data encoded and radiatedthrough the local oscillator 490 does not corrupt the data receivedthrough 500 into the receiver. Referring to FIG. 7b, the data input 470is input to microprocessor 480 which constructs a packet of digitizedinformation and timing bits, and periodically outputs this package tomodulate the local oscillator 490. The local oscillator 490 is,therefore, modulated by a packet formed by microprocessor 480 and,through the leakage radiation of local oscillator 490, the encodedinformation is radiated for receipt by a second receiving device. Dataencoded on signals radiated by the second receiver are received throughantenna 500 and input to mixer 510, which mixes the received signalswith the signal output by local oscillator 490. This produces signals atthe intermediate frequency containing a packet of information encoded bythe second receiver. If the local oscillator 490 is modulated at thesame time as the local oscillator in the second receiver, the resultingoutput data 540 determined from signals radiated by the second receiverdevice and received through antenna 500 and mixer 510 will be corrupted.By implementing the intelligent construction of packets, this will beavoided. Each packet constructed by microprocesor 480 will remain unsentto local oscillator 490 until a signal has been received from thedecoder indicating that reception of the incoming data from the secondreceiving device is complete. At this time, the information inmicroprocessor 480 will be sent to local oscillator 490 where the signalwill be modulated and radiated through leakage radiation to the secondreceiver. The second receiver, equipped in a like manner, will decodethe incoming information from the first receiver, recognize thatreception of the incoming data is complete and release the next packetto its local oscillator for radiation to the first receiver. Bysynchronizing the receiving devices in such a manner, the incoming datawill not be corrupted by the local oscillator of the receiver. Inoperation, this particular implementation will occupy twice the actualsignal bandwidth given a similar data range and a full-duplex system,since each signal is unmodulated for half the time during the time it isreceiving and not being modulated, but still radiating. Therefore, inorder to maintain a predetermined data rate, it is necessary to send thedata at twice the data rate.

In another implementation, the receivers are tuned to receive andtransmit on baseband and subcarrier whereby the signals received andradiated do not interfere with one another. This is described withreference to FIG. 8.

The receiver is configured to operate in one of two modes. The receivermay be configured to encode information into the subcarrier and receiveinformation encoded in the baseband, or vice versa. The configuration iscontrolled by placement of the switches 555 and 590. As shown in FIG. 8,the input (such as voice) is input to a subcarrier generator 560 whichis then input to local oscillator 565 to encode the input informationinto the subcarrier of the signal generated by the local oscillator 565.The output of the local oscillator 565 is input to network 570 whichdirects the signal to antenna 575 for radiation and to mixer 580.

A signal received through antenna 575 is input through the network 570to mixer 580. The output of the mixer 580, those signals at theintermediate frequency, are input to IF amplifier/detector 585. Switch590 controls the direction of the output of IF amplifier/detector 585.If the information received through antenna 575 was encoded into thebaseband, the outer part of IF amplifier/detector 585 is connected, viaswitch 590, to the output 595. If the information received throughantenna 575 was encoded into the subcarrier, the output of IFamplifier/detector 585 is connected to subcarrier detector 593 whichdetects the information encoded into the subcarrier and outputs it tothe output 595.

Thus, the information received, for example, encoded on the subcarrierand the information radiated, for example, encoded into the baseband, donot interfere with one another and data corruption due to the existenceof a modulated local oscillator (sidetone) is avoided.

As will be apparent to one skilled in the art by reading thisdescription, the numerous embodiments herewith described may be usedsingly to improve a proximal cable-less communication system or may beused in combination with one another. This is illustrated by thefollowing systems described.

A number of embodiments employing the techniques described herein areillustrated by FIGS. 9-13. In one embodiment, referring to FIG. 9a, datainput 600 modulates local oscillator 610 through a frequency synthesizercircuit 620 comprising frequency prescaler 630, frequency synthesizer640 and amplifier 650. The prescaler 630 scales or divides down thefrequency of the signal output by local oscillator 610 to a frequencyacceptable to the frequency synthesizer 640. The frequency synthesizer640 samples the frequency of the signal, compares the frequency to theideal frequency, as indicated by the tune command input 645, and outputsa control signal which is amplified by amplifier 650 and input to localoscillator 610 to adjust the frequency of the local oscillating signal.

The local oscillator used is a variable frequency oscillator. Althoughany variable frequency oscillator may be used, it is preferred that aparametrically tuned oscillator be used. This is described in patentapplication U.S. Ser. No. 07/477,680, filed Feb. 9, 1990, entitled"Parametrically Tuned Oscillator", now abandoned.

The modulated signal is output to an attenuator 670, amplifier 680,frequency multiplier 690 and amplifier 700. The frequency multiplier isused to increase the frequency to the frequency needed to be input tothe mixer 710 such that the desired IF is generated at the output of themixer. The frequency multiplier is illustrated as a frequency doubler,but may be a tripler or other value multiplier depending upon theapplication.

The output of amplifier 700 is input to a hybrid directional coupler 715which directs the modulated oscillating signal generated out to antenna720. The hybrid directional coupler 715 also causes the signal to beinput to band pass filter 730, amplifier 740 and mixer 710. The mixer710 is an unbalanced mixer which mixes the signal with the signalsdetected and received through antenna 720. The signals received byantenna 720 comprise the signals radiated by a second receiver deviceconstructed according to the proximal cable-less communication system ofthe present invention which is in close proximity to the presentreceiver device. The signals received by antenna 720 are then input to afilter 730 to eliminate those frequencies that do not contain theinformation radiated from the second receiver device. In the presentembodiment, the band pass filter 730 is designed to also pass the signalgenerated by local oscillator 610.

The intermediate frequency is set to a frequency high enough such that asimpler low cost filter may be used and the accuracy of the systemmaintained. The signals are then processed through an amplifier 740which amplifies the signals, thereby increasing the sensitivity of thereceiver.

The output of mixer 710 is input to a second portion of a doubleconversion circuit to extract the information radiated by the secondreceiver device. The signal output by mixer 710 is first input to afilter 750 which eliminates all but the signals operating at theintermediate frequency, which is the difference frequency of thefrequency of the local oscillator 610 and the frequency of the signalradiated by the second receiver device input to the mixer.

The signals output by filter 750 are input to an amplifier 760 and to asecond mixer 770 which mixes the signal with a signal generated by localoscillator 780. The second mixer 770 is used to bring the signalfrequency down to a level acceptable to the IF amplifier/detector 800.The output of mixer 770 is input through an IF filter 790 to filter allsignals but those at the second intermediate frequency into an IFamplifier/detector which detects the modulation of signals at the secondintermediate frequency, which are representative of the signal radiatedby the second receiver device. The output of the amplitude detector isinput to a simple comparator circuit 820 which generates a 1 or 0depending upon the value output by the detector 800. This results as thedata output 830 communicated by the second receiver device.

Alternatively, further signal preselection and amplification may beemployed to enhance the sensitivity of the receiver. This is illustratedby the block diagram of FIG. 9b and the corresponding circuit diagram ofFIG. 9c. FIGS. 9b and 9c illustrate a receiver device similar to thatillustrated by FIG. 9a, except that a second filter 717 and amplifier719 have been added to provide further preselection by elimination ofthe image frequency prior to input to the mixer and increasedsensitivity through the use of multiple filters and amplifiers. Thesignal frequencies to be processed may be more precisely detected andprocessed and elimination of extraneous signals may be more closelycontrolled.

Another embodiment of the proximal cable-less communication system ofthe present invention is illustrated by the block diagram of FIG. 10aand the corresponding circuit diagram of FIG. 10b. In this embodiment,the output of amplifier 700 is input directly to the mixer 710. However,the electrical interconnect between amplifier 700 and mixer 710 isdeliberately increased in length and routed along a predetermined pathin order to increase the effectiveness of radiation of the signalgenerated by local oscillator 610. The electrical interconnect isdeliberately routed to run parallel with the electrical interconnectthat connects antenna 720 with filter 730 for such a distance thatinductive coupling occurs and the signal traveling along the electricalinterconnect from the amplifier 700 to the mixer 710 induces a signal,at the point where the two electrical interconnects are parallel 850,onto the electrical interconnect connecting antenna 720 and filter 730,wherein the induced signal travels to antenna 720.

In the present embodiment, the signal generated by the local oscillator610 is input directly into the mixer 710, that is, the signal generatedby the local oscillator 610 is not input to the mixer 710 via the samesignal line which inputs the received signal to the mixer 710. Thebandpass filter 730 may then be configured to pass only those signals atthe predetermined frequency of the receiving signal, eliminating signalsat other frequencies, including signals at the frequency of the localoscillator (thereby eliminating front end overload).

The devices illustrated by FIGS. 9 and 10 are preferably operated in ahalf duplex manner wherein oscillator 610 is modulated according to thedata input 600 during a first time period to radiate signals which aresubsequently detected by a second receiver device. During a second timeperiod, the local oscillator 610 is not modulated and signals containinginformation radiated by a second receiver device are detected andreceived through antenna 720.

A receiver with a separate antenna feed is illustrated by the blockdiagram of FIG. 11a and the corresponding circuit diagram of FIG. 11b.The signal generated by local oscillator 810, is modulated according tothe data input 800 at a frequency controlled by the frequencysynthesizer circuit 820. The output of local oscillator 810 is input toan attenuator 870, amplifier 880, frequency doubler 890 and amplifier900. The output of amplifier 900 is input to a hybrid directionalcoupler 910 which produces the signal at two outputs of the coupler. Thesignal is output to antenna 920 which radiates the signal, and thesignal is output to mixer 925 preferably through an attenuator 912.Signals radiated by a second receiving device similarly configured aredetected and received by antenna 930. The signals received throughantenna 930 are input to band pass filter 940 to eliminate signals atfrequencies outside the frequency of the received signal including anysignals generated by local oscillator 810. This signal is then input toamplifier 950 which amplifies the amplitude thereby increasing thesensitivity of the receiver device. The mixer 920 is a balanced mixerwhich generates the sum and difference frequencies of the two inputfrequencies. The output of mixer 920 is input to filter 960 whichfilters out the frequencies resulting from the sum of the two inputsignals to the mixer and passes the difference frequency also referredto as the intermediate frequency.

The signals output from filter 960 are input to amplifier 970 and thento a second filter 975 before being input to a second mixer 980. Thesecond input to mixer 980 is a signal generated by local oscillator 990which preferably is tuned to a frequency which causes a differencefrequency at the output of the mixer to be generated which is infrequency range acceptable to and can be received by the IFamplifier/detector 1010. For example, if the local oscillator 810generates a signal at the frequency 1.2 GHz, which is subsequentlydoubled to 2.4 MHz by frequency doubler 890, and the local oscillator ofthe second received device generates a signal at 2.9 GHz, the outputsignal after filter 960 would be at a frequency of 50 MHz. The secondlocal oscillator 990 is set to generate signals at 48.5 MHz. Thus theintermediate frequency output from mixer 980 and filter 990 would be 1.5MHz, a signal frequency which can be processed by intermediate frequencyamplifier/detector 1010 and comparator circuit 1020.

The signals output by mixer 980 are signals at the intermediatefrequency encoded with the information radiated by the second receiverdevice. The signals are input to a second band pass filter 1000 whichsimilarly removes the frequencies which result due to the sum of the twoinput signals to the mixer 980. The filtered signals are then input intointermediate frequency amplifier/detector 1010 which, in conjunctionwith comparator circuit 1020, generates the data output 1030. By usingthe separate antenna, a more effective use is made of the localoscillator signal, thereby enhancing the robustness of the signal.

Throughout the structure of the present invention, more substantiallevels of local oscillator power may be used, such as those required toinject passive mixers to further enhance system robustness. The localoscillator could optionally simply be increased in power whilemaintaining the specifications for the receiver and attenuating thelocal oscillator signal to an acceptable power level at the mixer.

A full duplex digital system is shown in the block diagram of FIG. 12aand the corresponding circuit diagram of FIG. 12b. The local oscillator1050 for the receiver generates signals at a frequency controlled byfrequency synthesizer circuit 1065. The signals are attenuated byattenuator 2020 and amplified by amplifier 2030 and doubled in frequencyby frequency multiplier 2040. The frequency multiplier 2040 may or maynot be implemented depending upon the desired output frequency and thefrequency range of the local oscillator.

The data input 1070 is sent through a 0/180 phase shift circuit 1060which will cause, for example, an input of 0 to be shifted at 0° and aninput of 1 to be shifted 180° in phase. The shifted local oscillatorsignal is then sent through a coupling circuit or network 1080 whichsplits the signal and outputs a portion of the signal to antenna 2050for radiating the signal and also to attenuator 2060 and mixer 2070 ofthe receiver. The mixer 2070 produces signals which contain both thephase shift from its own local oscillator/data input circuit 1050, 1060and 1070 and the received signal with its phase shift representing thedata to be decoded.

The received signals are detected and received by antenna 2080 and areprocessed through incoming receiving filter 1090 and amplifier 2000. Theoutput of the balanced mixer 2070 are signals at the sum and thedifference frequencies of the two input signals. The output of the mixer2070 is then passed through a filter 2090, which eliminates the signalsat the frequency which are the sum of the frequencies of the two signalsand outputs those signals at the intermediate frequency throughamplifier 3000 and filter 3005 to a second mixer 3010.

The other input to the second mixer 3010 consists of a second phaseshift circuit controlled by the same common data input 1070 as the phaseshift circuit 1060. The phase shift circuit 3020 provides an opposingphase shift to the signals generated by the local oscillator 3015;namely, a 0 input causes a 180° shift in the output and an input valueof one causes a 0° shift. This inversely phase shifted signal iscombined with the intermediate frequency output by the second mixer3010, wherein the inversely phase shifted signal effectively cancels thephase shifted local oscillator signal present at the other input of themixer 3010. The result is that the output of the second mixer nowcontains only the desired signal received from the second receiverdevice without any kind of sidetone and thus contamination to the same.

This output of the mixer 3010 is input to an intermediate frequencyfilter 3030 which filters all but the desired frequencies containing theinformation to be detected by the IF amplifier/detector 3040. The outputof the filter 3030 is input to IF amplifier/detector 3040 which, inconjunction with comparator 3050, detects the data encoded in the signaland outputs the data as data output 3060.

Through this embodiment, the one effect of a full duplex system, namelyside tone, which tends to affect the state of the signal and corruptsthe information encoded thereon, is eliminated resulting in a moreaccurate and dependable reception of information.

A receiver device using baseband and subcarrier signals to eliminatesidetone are illustrated by FIGS. 13a and 13b. If the data to be encodedis encoded into the baseband, the data input 4000 is input throughswitch 4010, amplifier 4020 to local oscillator 4030. If the data input4000 is to be encoded into the subcarrier, the switch 4010 is connectedto the input of subcarrier generator/detector 4040. The subcarriergenerator and/or detector 4040 generates and encodes the input into thesubcarrier and outputs the subcarrier to amplifier 4020 to localoscillator 4030.

The output from mixer 4030 is input to attenuator 4040, amplifier 4050and hybrid directional coupler 4060 which, in the present example,directs the signal out to antenna 4070, to mixer 4080 and to frequencysynthesizer circuit 4090 for feedback and control of the localoscillator 4030.

The signals are received through antenna 4070 and input to mixer 4080through hybrid directional coupler 4060. Mixer 4080 is an unbalancedmixer, preferably a diode, which mixes signals received through antenna4070 and signals generated by local oscillator 4050.

The output of mixer 4080 is filtered by filter 4100 to eliminate all butthose signals at the intermediate frequency and amplified by amplifier4110 to provide increased sensitivity.

The signals output by amplifier 4110 are input to IF amplifier/detector4120 which detects the modulation of the signal at the intermediatefrequency and generates an output signal which comprises the informationencoded and radiated by the second receiver device. If the informationwas encoded into the baseband, the switch 4130 is positioned to directthe signal to the output 4140. If the information was encoded into thesubcarrier, the output of IF amplifier/detector 4120 is directed, viaswitch 4130, to the subcarrier generator and/or detector 4040 whichdetects the subcarrier information and outputs the output data to theoutput 4140.

By using the baseband and subcarrier to receive or radiate modulatedsignals, corruption due to sidetone is eliminated because theinformation being radiated, for example, through the baseband, isignored when detecting and decoding information encoded into thealternate means, in the present illustration, the subcarrier.

The invention has been described in conjunction with the preferredembodiment. Numerous alternatives, modifications, variations and useswill be apparent to those skilled in the art in light of the foregoingdescription.

We claim:
 1. In a proximal, cable-less communication system comprisingat least two receivers spaced a proximal distance apart, each receivercomprising an antenna for receiving an incoming signal, a mixer coupledto the antenna, a local oscillator coupled to the mixer which generatesan oscillating signal at a predetermined frequency, wherein the mixergenerates a signal at the difference frequency of the incoming signaland the oscillating signal, the local oscillator of the first receiverbeing modulated to provide the incoming signal to the second receiverand the local oscillator of the second receiver being modulated toprovide the incoming signal to the first receiver, such that eachreceiver receives the leakage radiation of the modulated localoscillator signal of the other receiver and information transfer isachieved by reception of the incoming signals, an improved proximalcable-less communication system, each of said receivers comprising:ahybrid directional coupler acting as an intentional signal path andhaving a first, second, third and fourth input/output ports, saidcoupler receiving as a first input through the first port a signalreceived from the other receiver, the first input being output throughthe third port to the mixer, said coupler receiving as a second inputthrough the fourth port the signal generated by the local oscillator ofthe, the second input being output to the antenna through the first portand to the mixer through the third port; whereby the primary function ofthe local oscillator signal to provide input to the mixer to generatethe intermediate frequency is maintained, the effectiveness of radiationis increased and the distance the receivers are spaced apart can beincreased.
 2. In a proximal, cable-less communication system comprisingof at least two receivers spaced a proximal distance apart, eachreceiver comprising an antenna for receiving an incoming signal, a mixercoupled to the antenna, a local oscillator coupled to the mixer whichgenerates an oscillating signal at a predetermined frequency, whereinthe mixer generates a signal at the difference frequency of the incomingsignal and the oscillating signal, the local oscillator of the firstreceiver being modulated to provide the incoming signal to the secondreceiver and the local oscillator of the second receiver being modulatedto provide the incoming signal to the first receiver, such that eachreceiver receives the leakage radiation of the modulated localoscillator signal of the other receiver and information transfer isachieved by reception of the incoming signals, an improved proximalcable-less communication comprising:an extended length signaltransmission line which couples the local oscillator to the mixerwhereby the signal transmission line provides opportunity along thelength of the signal transmission line for the leakage radiation tooccur, and the primary function of the local oscillator signal toprovide input to the mixer to generate the intermediate frequency ismaintained, the effectiveness of radiation is increased and the distancethe receivers are spaced apart can be increased; said extended lengthsignal transmission line being a minimum length of one-tenth of a signalwave length, and the distance the signal transmission lines areseparated by at least 0.1 inches, so that inductive coupling occurs andthe signal generated by the local oscillator on the extended lengthtransmission line is generated on the signal transmission line whichcouples the antenna and the mixer.
 3. The proximal, cablelesscommunication system as described in claim 2, wherein the length of theextended length signal transmission line is located to lie parallel witha signal transmission line which couples the antenna and the mixer, thelength of the signal transmission lines being long enough and thedistance the signal transmission lines are separated being short enoughsuch that inductive coupling occurs and the signal generated by thelocal oscillator on the extended length transmission line is generatedon the signal transmission line which couples the antenna and the mixer,whereby the signal generated by the local oscillator is output to theantenna for output thereby increasing the effectiveness of radiation ofthe signal.
 4. The proximal, cable-less communication system asdescribed in claim 3, wherein the minimum length of the signaltransmission lines is one-tenth of the signal wave length.
 5. Theproximal, cable-less communication system as described in claim 3,wherein the spacing between the signal transmission lines is 0.1 inches.6. The proximal, cable-less communication system as described in claim3, wherein the signal is at a frequency of 2.4 GHz, the signaltransmissions lines are parallel for a distance of 0.5 inches and thespacing between the signal transmission lines is 0.1 inches.
 7. In aproximal, cable-less communication system comprising of at least tworeceivers spaced a proximal distance apart, each receiver comprising afirst antenna for receiving an incoming signal, a mixer coupled to thefirst antenna, a local oscillator coupled to the mixer which generatesan oscillating signal at a predetermined frequency, wherein the mixergenerates a signal at the difference frequency of the incoming signaland the oscillating signal, the local oscillator of the first receiverbeing modulated to provide the incoming signal to the second receiverand the local oscillator of the second receiver being modulated toprovide the incoming signal to the first receiver, such that eachreceiver receives the leakage radiation of the modulated localoscillator signal of the other receiver and information transfer isachieved by reception of the incoming signals, an improved proximalcable-less communication system, each of said receivers comprising:asecond antenna for radiating the signal generated by the localoscillator; means for splitting the local oscillator signal generated bythe local oscillator to be output to a second antenna, separate from thefirst antenna which receives the incoming signal, while concurrentlyproviding the local oscillator signal as input to the mixer; whereby theprimary function of the local oscillator signal to provide input to themixer to generate the intermediate frequency is maintained, theeffectiveness of radiation is increased and the distance the receiversare spaced apart can be increased.
 8. The proximal, cable-lesscommunication system as described in claim 7, wherein said means forcausing the signal generated by the local oscillator to be output to thesecond antenna comprises a signal splitter which splits the signalgenerated by the local oscillator between the mixer and the secondantenna.
 9. The proximal, cable-less communication system as describedin claim 7, wherein said first and second antennae are located adistance apart to decrease the effect of the signal generated by thelocal oscillator on the signals received through the first antenna. 10.The proximal, cable-less communication system as described in claim 9wherein the first and second antennae are spaced apart a minimumdistance of one-half the wavelength of the signal generated by the localoscillator.
 11. The proximal, cable-less communication system asdescribed in claim 10, wherein the signal generated by the localoscillator is at a frequency of 2.4 GHz and the first and secondantennae are spaced apart a minimum distance of 2.4 inches.
 12. Theproximal, cable-less communication system as described in claim 7,wherein the first antenna is at a polarization different from the secondantenna.
 13. The proximal, cable-less communication system as describedin claim 12, wherein the first antenna is horizontally polarized and thesecond antenna is vertically polarized.
 14. The proximal, cable-lesscommunication system as described in claim 7, wherein the first andsecond antenna are of different lengths, the second antenna being longerthan the first antenna to more efficiently radiate signals generated bythe local oscillator.
 15. The proximal, cable-less communication systemas described in claim 7, wherein the first and second antennae arelocated to be co-linear to one another.
 16. The proximal, cable-lesscommunication system as described in claim 7, wherein the first antennais tuned to the frequency of the received signal and the second antennais tuned to the frequency of the signal generated by the localoscillator.
 17. In a proximal, cable-less communication systemcomprising of at least two receivers spaced a proximal distance apart,each receiver comprising a horizontally polarized first antenna forreceiving an incoming signal, a mixer coupled to the first antenna, alocal oscillator coupled to said mixer which generates an oscillatingsignal at a predetermined frequency, wherein said mixer generates asignal at the difference frequency of the incoming signal and theoscillating signal, the local oscillator of the first receiver beingmodulated to provide the incoming signal to the second receiver and thelocal oscillator of said second receiver being modulated to provide theincoming signal to said first receiver, such that each receiver receivesthe leakage radiation of the modulated local oscillator signal of theother receiver and information transfer is achieved by reception of theincoming signals, an improved proximal cable-less communication system,each of said receivers comprising:a vertically polarized second antennafor radiating the signal generated by the local oscillator; a signalsplitter which splits the local oscillator signal generated by the localoscillator between the mixer and the second antenna, separate from thehorizontally polarized first antenna which receives the incoming signalby a minimum distance of one-half the wavelength of the signal generatedby the local oscillator, while providing the local oscillator signal asinput to the mixer; whereby the primary function of the local oscillatorsignal to provide input to the mixer to generate the intermediatefrequency is maintained, the effectiveness of radiation is increased andthe distance the receivers are spaced apart can be increased.
 18. Theproximal, cable-less communication system as described in claim 17,wherein the first and second antenna are of different lengths, thesecond antenna being longer than the first antenna to more efficientlyradiate signals generated by the local oscillator.
 19. The proximal,cable-less communication system as described in claim 17, wherein thefirst and second antenna are located to be co-linear to one another. 20.The proximal, cable-less communication system as described in claim 17,wherein the first antenna is tuned to the frequency of the receivedsignal and the second antenna is tuned to the frequency of the signalgenerated by the local oscillator.
 21. In a proximal, cable-lesscommunication system comprising of at least two receivers spaced aproximal distance apart, each receiver comprising an antenna forreceiving an incoming signal, a mixer coupled to the antenna, a localoscillator coupled to the mixer which generates an oscillating signal ata predetermined frequency, wherein the mixer generates a signal at thedifference frequency of the incoming signal and the oscillating signal,the local oscillator of the first receiver being modulated to providethe incoming signal to the second receiver and the local oscillator ofthe second receiver being modulated to provide the incoming signal tothe first receiver, such that each receiver receives the leakageradiation of the modulated local oscillator signal of the other receiverand information transfer is achieved by reception of the incomingsignals, an improved proximal cable-less communication system, each ofsaid receivers comprising:an extended length signal transmission linewhich couples the local oscillator to the mixer lies parallel with asignal transmission line which couples the antenna and the mixer, thelength of the signal transmission lines being a minimum length ofone-tenth of a signal wave length, and the distance the signaltransmission lines are separated by at least 0.1 inches, so thatinductive coupling occurs and the signal generated by the localoscillator on the extended length transmission line is generated on thesignal transmission line which couples the antenna and the mixer;whereby the signal generated by the local oscillator is output to theantenna for output thereby increasing the effectiveness of radiation ofthe signal and the spacial distance between the receivers.